title: 1-(3-Carboxyl-atophen-yl)-4,4'-bipyridin-1-ium dihydrate.
abstract: In the crystal structure of the title compound, C17H12N2O2·2H2O, the carboxyl-ate group is linked via O-H⋯O hydrogen bonds to two water mol-ecules. The crystal packing is best described as parallel layers (viewed along the a axis) of viologen and water mol-ecules associated via O-H⋯O hydrogen bonds and π-π inter-actions, with a centroid-centroid separation of 3.8276 (9) Å.
authors.affiliation: Key Lab for Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, People's Republic of China.
authors.forename: Mengchan
authors.initials: M
authors.lastname: Fan
authors.forename: Zhenguo
authors.initials: Z
authors.lastname: Yao
authors.forename: Chen
authors.initials: C
authors.lastname: Li
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Fu